Spark plug exploded in engine

Post by **jcgirton** » 16 Apr 2017, 11:04

So i have a 2002 Volvo S60 2.4t - the other day driving home from work it started running really rough. I drove it home figuring possibly one of the coil packs were bad. I bought new ones and went out to swap them and pulled the first one out and to my surprise the ceramic end of the spark plug looked like it exploded - I'm assuming I cant just replace it and drive it because the ceramic could be in there, I'm also assuming if the ceramic made it out of there, it could have wound up in the turbo (is that possible?) The car has 312,000 miles on it. I'm assuming I should have the engine taken apart to fish the ceramic out and see if there was additional damage - I'm looking for advice if I should try to do that or possibly just replace the whole engine because of the miles? Also does anyone know approximately how much either should cost?

Post by **Botbasher** » 16 Apr 2017, 11:34

If you want to see what you can do before you invest, I'd suggest one of those little Endoscopes for the cell phone that will happily get into the cracks and corners of the cylinder. I have one and they are awesome for engine work and gunsmithing. If you're not just going to replace it, I'd suggest that before rotating the motor any more.

Odds are that the pieces went in... bounced around a few hundred times... and did their damage before escaping into the exhaust system. Seen this happen a couple of times and it's not usually pretty.

Good luck!

KS

Post by **jcgirton** » 16 Apr 2017, 13:21

So I'm stupid - the only part of the spark plug that actually came off was the little end part that you gap... i put a new spark plug in to see what happened and it seems like the spark plug is stripped, the old one came out with the coil pack so it wasn't even in... previously i just hand tightened them and then did 1/4 turn with a wrench... I'm assuming it stripped when it got pushed out? any reason why it would have gotten pushed out?

Post by **oragex** » 16 Apr 2017, 13:35

Not impossible the plug had just loosened up by itself with all the explosions and vibrations inside the cylinder. For new plugs with the washer still intact I believe it's more like 3/4 turn from memory. It should be written on the package. For old plugs with the washer crushed, it has to be felt by hand. It is a feeling thing, just don't over-tighten and never remove/install a plug on a hot engine - the threads are much more fragile because the aluminum is less strong when hot. It is always possible a previous mechanic had damaged the threads.

Post by **jcgirton** » 16 Apr 2017, 14:25

So if i just have a mechanic install something like a helicoil plug it should be okay? any idea how much that may run approximately?

Post by **JDS60R** » 16 Apr 2017, 17:09

It sounds like the metal part of the spark plug is fine and your ceramic insulator that goes into the combustion chamber is missing.
If so,
Remove the spark plug and disconnect the fuel injector for that cylinder. Start it and let it run for about 15 seconds. Everything will come out the spark plug hole or out the exhaust valve. Then replace the spark plug and plug the injector back in. It is impossible for it to get back to the turbo so don't worry about that. It is likely that the plug was effected by lean burning condition or the ceramic was cracked before or during installation. Check the new plug in a few days for its color and post a pic so we may advise you on if it seems it is running too lean. At 300+K it is not rare to have a clogged or dirty fuel injector causing lean running condition. It is rare to have the ceramic brake but I have seen about 20 of them over the last 35 years of tuning stock cars. It is much more common on modified, high boost, high hp cars.

Post by **Botbasher** » 16 Apr 2017, 19:59

JDS60R wrote: ↑16 Apr 2017, 17:09 ... It is impossible for it to get back to the turbo so don't worry about that....

Ummmm Errrrrrr.... Ahem. The next stop after passing the exhaust valve IS the Turbine! Anything that goes out the exhaust port is hitting the wheel!!

Only saving grace here, is that it either already did it's damage, or the 15 sec run you suggested at idle will let any bits pass without harm as the turbine, at that RPM, shouldn't be harmed but anything as small as a spark plug electrode. Alternately, and I probably would till you're sure nothing more (like ring lands and such) you could wedge the wastegate open and allow everything to bypass the turbine while testing these theories! It's not a sure thing, but it's a better odds thing.

I would still visualize it if you intend on keeping the motor for any appreciable length of time. Just for your own sanity when you merge onto a busy freeway.

If you don't buy or borrow an endoscope (think Autozone loans them), at least do a compression check. If that metal bit got crushed into the valve seat you could be turning over a ticking time bomb.

Good Luck!

KS

Post by **JDS60R** » 16 Apr 2017, 21:16

Bot is correct . If it goes out the exhaust valve it can go by the wheel (or by the waste gate opening) on the exhaust side. My brain took "runs "back" to the turbo and focused on the compressor side. My mistake - Good catch Bot (KS)

Post by **abscate** » 17 Apr 2017, 05:08

Take the plug out, vacuum the cylinder with a good strong shop vac, breaking and making the vacuum several times. Listen for bits getting sucked up too.

Then crank it over with the plugs out several times. Pull fuel pump relay first.

If you are karmic, that will get rid of the nasty stuff, new plugs and good to go.

pappy76 · Post by **pappy76** » 15 Aug 2019, 23:34

So this exact thing has happened to me with my 06 s60r. Driving on the highway the other day, car starts missing(running rough). Get it home and hook up VIDA. Misfire cylinder 2. Take off the plastic harness cover. Theres oil everywhere. Just recently had head rebuilt for bad exhaust valves. So they apparently put on upper pcv hose half assed and not straight, so it had been slowly leacking for what would be about three months since the repair. Enough time to fill in all the indents on top off the engine and submerge already frayed coil wires, which I believe is why the spark plug blew up. So same as OP, I find the ceramic end and probably half inch of electrode has gone into the cylinder. So I rent a borescope and cant see anything. I try vaccuming as suggested. Nothing. So I think maybe it's already gone through and done its damage and proceed to install a new plug. After cleaning up all the oil and remounting the pcv hose correctly. I start her up. I immediately here a couple metal taps, then I really here taps like the electrode has found it's way to the wheel in my turbo. I immediately shut her down. At this point I'm mortified. I just spent over 2000 grand having this garage pull the head, have it rebuilt and put it back on. So I'm assuming I should pull the turbo. The mention about opening wastegate, sounds doable, but should I just not take the chance on any more damage and just pull it off.